MDA is designed as a test bed for an astrobiology field instrument to detect microbial metabolic activity in terrestrial or extraterrestrial geological soil samples. MDA employs electrochemical sensors in a unique differential chamber configuration, able to detect minute changes in the chemical composition between the two otherwise identical chambers. Both chambers are filled with identical autoclave-sterilized, sample-water mixtures. Only one of the chambers receives an additional minute, non-sterilized inoculation sample. Under the minimal assumptions that the geological sample contained nutrients (energy), organisms, and required water to initiate growth, the differential electrochemical measurements would now allow detection of metabolic activity, in addition to the electrochemical characterization of the soil samples in both chambers.